Lee

Eric, I sent you a long reply to your PM but your mailbox is full.

red racer

Thought I would step in at the end...

I saw the difference 8.0mm (Blue) and 8.5mm (Red). It is all
about the resistance that each wire has per foot. When I looked
at both the 8.5mm had a less resistance per foot allowing more
spark to reach the plug.

Yes, the insulation is not an issue in the marine engines, but
usually the bigger the isulation allows the automotive wires
to retain their low resistance when heat is applied through the
headers.

My speed shop had the differences listed when I bought my
set. The "Reds" were listed at 40 - 50 ohms per foot. They added
that the standard wires had 5 - 10x the resistence.

Anyway, red fits my attitude...

Tonto

So, what's wrong with the Mercruiser ignition? Simple and it works.
Robert

US1 Fountain

A blast from the past.......

Ok, heres the deal.

I installed the MSD 8MM Heli Coil wires this spring, replacing my Merc original wires, and a MSD Blaster coil. Still using the Merc ignition T-bolt IV (no knock sensor).

I also have lost 500 rpm this year=loss of speed too!

Just got in from checking the ohms on both the MSD and Merc wires for comparison.
24" wire length results:

MSD - 2.201 k ohms (MSD specs 150-1200 ohms/ft)
Merc- 11.63 k ohms

Without reinstalling my old wires, what do these numbers say to the more intelligent than myself? Not even sure if I can read the ohm meter! Can the MSD wires be a cause for my loss of rpm?

Thanks,
Jerry

Iggy

Looking at your measurements, the MSD's have a lower resistance than the Merc's.
2.2K ohms is not bad. "0" ohms would be better.
Remember "K' stands for "kilo" whitch is equivelant to 1000.
You say MSD claims a 150-1200 (1.2K) per foot? That's a wide range of resistance. 1200 ohms is 8 times higher resistance than 150 ohms.

I can't figure out why it would cause a drop in RPM.
Unless the low resistance is somehow reducing the spark voltage. But lower resistance should allow a higher voltage to be available to the plug.
I'll have to think about this.

ForrestC

Magnecor makes the best ignition wires, but they cost big bucks! If you have a few minutes, check out there website. You will lots of really good info on ignition wires over there.

Check out the section on "low-resistance spiral-core wire"

CheckmateF1

Jerry, I was just wondering if you switched back to your old wires or not. Have you found your 500rpms?

Thanks, Eric

US1 Fountain

Hey Eric,

Still around I see.

No, haven't changed anything yet. Not sure if I want to jinx myself this late in the season. I'm kicking around the idea of different heads and no blower. Ran on the Ohio last weekend and gas just about did me in. Don't think I could have poured it overboard as fast as it was burning it. Checked against GPS and avg. around 1.4 mpg. Going to contact JimV this winter for his thoughts. New heads or wedges. Have to get some idea of $$. I think we both lost our rpms from the head work done. That was the only modification done to my motor this winter, so..........

Jerry

CheckmateF1

Yes Im still around. I may be selling the boat but I doubt I can leave OSO!

I agree with ya. It's gotta be in the heads. You might want to talk to Mr Gadgets if your gonna go with JimV heads. I think he has them.



talk soon, Eric

Tinkerer

I have run three sets of Jim's heads and have been very happy with his work. They do produce GOOD HP. When it comes to heads Jim knows his stuff.